Fine particles of cellulose exist in water in a colloidal state and show properties of various stabilizers and body imparting agents as disclosed in Industrial And Engineering Chemistry, vol.54, pp.20-29 (1962). That is, the fine cellulose particles have a number of hydroxyl groups on the surface thereof, which hydroxyl groups provide a hydrate structure to give a stable colloidal cellulose when dispersed in water.
An example of a water-dispersible complex utilizing this property of cellulose is described in JP-B-40-12174 (the term "JP-B" as used herein means an "examined published Japanese patent application"). There, an aqueous colloid dispersion is obtained by adding an interfering agent to a united body of cellulose crystallites. Also, JP-B-56-31094 and JP-B-57-14771 disclose a water-dispersible complex composed of a combination of fine crystal cellulose with a dispersing agent or a disintegrator. According to these conventional techniques, water dispersible complexes are obtained by mixing cellulose particles with a water-soluble polymer, saccharide, etc., in the presence of water, and then grinding the mixture, followed by drying and pulverizing the ground mixture.
However, the cellulose dispersion obtained from the complex thus prepared has an extremely sandy texture. Therefore, when this complex is used as a stabilizer for foods, etc., it is necessary to increase the addition amount thereof to obtain satisfactory performance as a colloid. As a result, the viscosity is increased because of a water-soluble polymer and original taste of the food is lost. Alternatively, the complex or the food to which the complex is added is treated with a homogenizer having a strong dispersing faculty. But, in this case, there is a restriction on the dispersing means employed and also there is a limit on the increase of the colloid performance.
Also, a dispersion obtained from the complex has a small colloid fraction and includes coarse particles because of an insufficient attrition effect on the cellulose particles. Therefore, there is the problem of precipitation of the coarse particles when the dispersion is used in materials having a relatively low viscosity, such as beverages. Also, a sandy feeling is caused in food additives wherein importance is attached to the taste of food. Moreover, there is a limitation on the use thereof in materials wherein a smooth aftertaste and apparent texture are required. Additionally, there is a problem of clogging fine pipes and screens during transporting the slurry.
Thus, efforts have been made to develop sufficiently fine cellulose particles to solve these problems. For example, EP-0415193A2 discloses a water dispersion of cellulose particles having an average particle size of not larger than 6 .mu.m; WO-9102461 and U.S. Pat. No. 5,011,701 disclose a method for making fine cellulose particles for use in low-calorie cheese; and JP-B-62-30220 discloses a method for making uniform a suspension of fine cellulose crystalline.
However, in these techniques, the fine cellulose particles are stored and used in the form of an aqueous slurry, and hence there are large restrictions on the usage thereof. That is, there is the problem that microorganisms generate during storage. Transportation in the form of aqueous slurry is troublesome. Also, the aqueous slurry cannot be used at a high concentration. Thus, the techniques disclosed in the foregoing patents are unsatisfactory. When these fine cellulose particles are dried along with the aforementioned interfering agents, etc., to obtain a complex, a sufficient dispersion cannot be obtained when the complex is re-dispersed in water.